noun
over-the-counter drug; OTC medicine
Refers to medicine bought directly at a pharmacy without a prescription. Often contrasted with 売薬 (ばいやく), which can also mean OTC drugs but from the seller's perspective.
See also: 売薬
風邪のときは、まず買い薬で様子を見ます。
When I have a cold, I first see how it goes with over-the-counter medicine.
この症状なら、買い薬で十分
For these symptoms, an OTC drug should be enough.
売薬 also means over-the-counter medicine, but it emphasizes the seller's side (medicine for sale). 買い薬 focuses on the buyer's perspective (medicine bought without prescription).
処方薬 is a prescription drug, which requires a doctor's prescription, unlike 買い薬.
Compound of 買い (kai, 'buying') + 薬 (kusuri, 'medicine'). The reading ぐすり is a rendaku form of くすり.